Wireless power feeder and wireless power transmission system

Abstract

Power is fed from a feeding coil L 2 to a receiving coil L 3 by magnetic resonance. An oscillator 202 alternately turns ON/OFF switching transistors Q 1 and Q 2 to cause AC current IS of drive frequency fo to flow in a transformer T 2 primary coil Lb. The AC current IS causes AC current I 1 to flow in an exciting coil L 1 and causes AC current I 2 to flow in the feeding coil L 2.

What is claimed is: 
     
       1. A wireless power feeder for feeding power from a feeding coil to a receiving coil by wireless using a magnetic field resonance phenomenon between the feeding coil and receiving coil, comprising:
 a power transmission control circuit that includes first and second current paths and makes first and second switches connected in series respectively to the first and second current paths alternately conductive to feed AC power to a first coil included in both the first and second current paths; 
 the feeding coil; and 
 an exciting circuit in which a second coil magnetically coupled to the first coil and an exciting coil magnetically coupled to the feeding coil are connected, wherein 
 the exciting circuit receives AC power from the power transmission control circuit through the second coil and feeds the AC power to the feeding coil through the exciting coil. 
 
     
     
       2. A wireless power feeder for feeding power from a feeding coil to a receiving coil by wireless using a magnetic field resonance phenomenon between the feeding coil and receiving coil, comprising:
 a power transmission control circuit that includes first and second current paths and makes first and second switches connected in series respectively to the first and second current paths alternately conductive to feed AC power to a first coil included in both the first and second current paths; and 
 a feeding coil circuit in which the feeding coil and a second coil are connected, wherein 
 the feeding coil circuit receives AC power from the power transmission control circuit through the second coil magnetically coupled to the first coil. 
 
     
     
       3. The wireless power feeder according to  claim 2 , wherein
 the power transmission control circuit includes: 
 a bridge rectification circuit in which diodes are bridge-connected at four first to fourth connection points; 
 an AC power supply connected between the first and second connection points of the bridge rectification circuit; and 
 a capacitor connected between the third and fourth connection points of the bridge rectification circuit and charged by the AC power supply, wherein 
 the power transmission control circuit feeds AC power to the first coil using the capacitor as a DC voltage source. 
 
     
     
       4. The wireless power feeder according to  claim 3 , wherein two capacitors are connected in series between the third and fourth connection points, and the midpoint of the capacitors is connected to one of the first and second connection points. 
     
     
       5. The wireless power feeder according to  claim 4 , comprising a switch for controlling electrical conduction of a path extending from the midpoint to one of the first and second connection points. 
     
     
       6. The wireless power feeder according to  claim 2 , wherein the number of windings of the first coil is greater than that of the second coil. 
     
     
       7. The wireless power feeder according to  claim 2 , wherein input voltage of the power transmission control circuit is applied to one of a series circuit composed of the first coil and the first switch and a series circuit composed of the first coil and the second switch. 
     
     
       8. The wireless power feeder according to  claim 2 , wherein the power transmission control circuit makes the feeding coil that does not substantially resonate with circuit elements on the power feeding side feed the AC power to the receiving coil. 
     
     
       9. The wireless power feeder according to  claim 2 , wherein the power feeding coil does not form, together with the circuit elements on the power feeding side, a resonance circuit having a resonance point corresponding to the resonance frequency of the receiving coil. 
     
     
       10. The wireless power feeder according to  claim 2 , wherein no capacitor is inserted in series or in parallel to the power feeding coil. 
     
     
       11. The wireless power feeder according to  claim 2 , wherein the feeding coil is connected to a capacitor and form a circuit which resonates at a resonance frequency of the receiving coil. 
     
     
       12. A wireless power transmission system comprising:
 a wireless power feeder as claimed in  claim 2 ; 
 the receiving coil; and 
 a loading coil magnetically coupled to the receiving coil and receives power that the receiving coil has received from the feeding coil. 
 
     
     
       13. The wireless power transmission system according to  claim 12 , wherein the receiving coil is connected to a capacitor and form a circuit which resonates at a resonance frequency of the feeding coil circuit.